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31 Cards in this Set

  • Front
  • Back
What is the delayed type hypersensitivity reaction seen in a previously exposed person to TB an example of?
CD4+ Tcells responding to the protein challenge, with 2-3 days later a subsequent inflammatory reaction to get rid of it.
How do Thelper cells induce an inflammatory reaction?
By activating macrophages with IFN-y and CD40L/CD40 binding.
When you inject a PPD of TB, what is the first step?
Macrophages ingest the protein and display it on MHCII.
What is this immune response called?
The initial, innate response.
What cells respond to this MHCII presentation of peptide?
Thelper 1 cells
What happens to the Th1 cells upon recognition of the antigen?
-Upregulation of CD40L
-IFN-y secretion
What is the purpose of IFN-y secretion and CD40L expression?
To further activate the macrophages that presented the Ag in the first place.
Why would you want to activate macrophages?
Because they can kill the microbes being presented if their ROI/NO generating mechanisms are ramped up.
What do activated macrophages secrete?
-TNF, IL-1, chemokines, and IL-12.
What are the functions of TNF and IL-1?
To increase the affinity and expression of CAMs on endothelial cells and T cells.
What majorly important molecules are upregulated and expressed on APCs in response to IFN-y and CD40/CD40L binding?
B7 - the costimulatory molecule.
What is the function of the IL-12 secreted by activated macrophages?
It induces more naive CD4+ cells to differentiate into Th1 cells; creates a positive feedback loop as these then activate more APCs via IFN-y, they secrete more IL-12, and on and on.
So what dangerous potential is there in the TH1 inflammatory reponse?
It could become chronic if the stimulus antigen is not removed.
So list 4 categories of things turned on in activated macrophages:
1. NO/ROI's
2. TNF, Il-1, Il-12, chemokines
3. B7
4. MHC I and II
What happens to macrophage secretions once the pathogen is eliminated?
It starts to release cytokines and growth factors like PDGF to start healing.
What causes Th cells to differentiate into Th2 cells?
What is the source of IL-4?
What do Th2 cells secrete?
-IL4, IL5, and IL10
What do Th2 cytokines do?
-Inhibit macrophage activation
-Causes class switching of plasma cells to IgE
-Activates Eosinophils to aid in mast cell response
What pathogens are CD8 CTLs directed against?
-Intracellular in cytoplasm
-Those that escape phagolysosomes
Do CTL effector cells require costimulatory signals?
What does CTL activation lead to?
-Perforin release
-Granzyme release
What surface marker on CTLs allows them to kill infected cells without perforin/granzyme release?
What cells express Fas receptor?
Host cells infected with virus
What are the 2 ways by which NAIVE CD8 Tcells are activated?
1. Direct
2. Indirect
What is the direct way to activate naieve CD8 Tcells?
1. MHC Class I presents Antigen
2. Costimulatory signal
-Activates, proliferates via IL2, and differentiates into CTL.
What is the Indirect way to activate naive CD8 Tcells?
1. APC presents antigen on MHCI
2. not enough costimulatory sig
Thelper cells helps by activating the APC (CD40/CD40L upregulates B7 expression)
What is the indirect activation of naive Tcells an example of?
CD4-CD8 cooperation
If the APC doesn't express enough B7 to stimulate the CD8 cell, how can it stimulate the CD4 cell?
i dont know
Do CTLs get killed along with the target cells, when they release perforin and granzymes?
No; they release and stay at the infection site to kill other target cells.
How do granzymes kill the target cells exactly?
By activating caspases which induce apoptosis.